1. Field of the Invention
This invention relates to conveyors for material handling applications and more specifically to conveyor support frame construction.
2. Description of the Related Art
Various different types of conveyor systems are used to transport various types of materials between designated locations. The typical conveyor includes a conveyor medium such as rollers, belt or continuous chain movably supported on a support frame and driven by a suitable power source. The conveyor support frame typically includes parallel side frames and cross members interconnecting the side frames to support rollers or other conveying medium. A design problem common to conveyor frame construction is the need to keep the frame properly aligned, by keeping the side frames in a fixed relation to each other, in the presence of missaligning forces generated by movement of the conveyor medium under load. Misalignment causes excessive wear of the conveyor components, such wear is expensive not only in the cost of the components but also in conveyor down time required to replace the components. Furthermore, lack of proper alignment may cause materials transported by the conveyor to be misdirected or damaged.
It will be apparent that conveyor frame construction will differ between conveyors carrying heavy loads and those carrying light loads. In warehousing operations smaller, lighter weight conveyors are typically used only to transport units typically weighing less than 100 pounds each, while larger conveyors are used to transport large pallets weighing several thousands of pounds. Maintaining proper alignment is much more of a problem in the larger conveyors because of the heavier loads and typically, the greater spacing between the conveyor side walls. Prior art lightweight conveyors may employ tie rods or tubes as cross members, bolted to the side frames. Standard J-bolts or hook-bolts, having a hook portion forming more nearly an acute angle with the shaft portion than a typical J-bolt, have been used to connect cross members to the side frames of lightweight conveyors. Heavy conveyors, such as those used to transport loaded pallets, typically employ a welded construction in which cross members are welded to the side frames to ensure continued alignment of the conveyor frame during use. A serious disadvantage of welded conveyor frame construction, however, is that the conveyor support frame must be welded in a conveyor assembly area and thereafter painted in a separate paint area and must then be returned to the assembly area for further assembly. This additional handling is labor intensive and adds significantly to the cost of the conveyor. Bolted construction conveyor frames have a significant advantage in that the conveyor side walls and cross members may be individually painted as component parts and the complete conveyor can be assembled from the component parts all in one assembly area.